Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $92.91   4.351%   $96.9525   $96.95   $96.95   $97.00  
  Purchase #2 $139.90   3.293%   $144.5069   $144.51   $144.50   $144.50  
  Purchase #3 $249.67   3.830%   $259.2324   $259.23   $259.25   $259.20  
  Purchase #4 $133.99   4.871%   $140.5167   $140.52   $140.50   $140.50  
  Purchase #5 $80.97   6.779%   $86.459   $86.46   $86.45   $86.50  
  Purchase #6 $203.73   13.218%   $230.659   $230.66   $230.65   $230.70  
  Purchase #7 $57.59   11.397%   $64.1535   $64.15   $64.15   $64.20  
  7 purchase totals = $958.76       $1,022.4800   $1,022.48   $1,022.45   $1,022.60